1. Field of the Invention
The present invention pertains to the charging of capacitors used with defibrillators, and in particular external defibrillators.
2. Description of the Related Art
Cardiotherapeutic defibrillators, once used only by trained medical personnel, are now being made available for use by the general population, including individuals having little or no training. The defibrillators contemplated for general use are of the automatic external type and include on-board real time diagnostic capability to intervene or otherwise control the defibrillator therapy being administered. In general, the defibrillators deliver a relatively high voltage, low energy pulse or series of pulses to a patient suffering cardiac arrhythmias, such as ventricular fibrillation. The power supply relied upon to deliver the defibrillation therapy typically comprises one or more batteries carried on board the defibrillator unit or an electrical power utility supplying mains power to a building, for example.
Because of the nature of the electrical therapy required, it is not possible in a practical device to supply the therapeutic energy upon instantaneous demand, by drawing from the power source. Instead, energy from the power source must be accumulated over a certain period of time in one or more defibrillator capacitors which are later discharged to deliver the desired defibrillation therapy. It is particularly critical that the defibrillation therapy be delivered as quickly as possible, given the nature of the medical threat encountered. Accordingly, rapid charging of the defibrillator storage capacitor is required and advances in reducing charge time are still being sought.
Due to the nature of the use to which the defibrillation equipment is put, certain components employed must be carefully constructed to close performance tolerances which are expected to be closely maintained throughout the life of the component. It is important that such components are not unexpectedly stressed during unusual operating conditions, as when main power supply voltage unexpectedly drops. Also, it would be advantageous if a closer control could be exercised over the stress to which the electrical components are put.